The purpose of this series is to bring casual soccer fans up to speed on the interesting aspects of world -- and especially British -- soccer. In previous posts, you have read about the Premier League, promotion and relegation, World Cup qualifying, and more. In this post, we tackle the EFL Cup.

Premier League matches are usually played on the weekends, with sporadic international breaks. In the middle of the week, various competitions take place. The most notorious are the Champions League and the Europa League -- European competitions that we have highlighted in past posts. About once per month, though, the middle of the week is, instead, filled with more matches between English clubs.

That's the EFL Cup.

EFL Cup Format

The EFL Cup is a tournament for professional British soccer teams. In our promotion and relegation post, we discussed the different tiers of British soccer. The top four tiers are basically considered to be the professional tiers. Clubs in those top four leagues have squads of players who basically make soccer their careers.

They all play in their own leagues, but the EFL Cup brings them all together. All 92 clubs in the top four English leagues play in this open tournament.

The clubs play one knockout match in each round. If the score is tied after 90 minutes, the match goes to extra time and, maybe, penalty kicks.

At the end of the whole thing, the winner of the tournament wins the EFL Cup.

Different EFL Cup Names

The EFL Cup has had several different names throughout the years. Usually, the tournament takes on the name of its primary sponsor. That is why in the last decade it has been called the Carling Cup and the Capital One Cup.

Some people just called the League Cup. That is a sufficient name to represent that this is a tournament of British soccer clubs in the professional leagues.

For the first time this year, it is known as the EFL -- English Football League -- Cup.

EFL Cup Surprises

At a minimum, every professional British club plays in at least three competitions each year: the league season, the EFL Cup, and the FA Cup (this will be written about in a future post). The top clubs also have to navigate through either the Champions League or the Europa League as well.

This makes the season extremely difficult for players. They are either used to playing only on the weekends or they are also playing most weekends and mid-weeks already because of European competition.

As a result, the EFL Cup sometimes takes a back seat. When Premier League managers rank their priorities each year, the EFL Cup is almost always listed last. This often leads to seeing plenty of backups in the squads and some surprise results.

Take February 2013, for example. The final of the League Cup was between Swansea City -- a mid-table Premier League side at the time -- and Bradford City -- a League Two team (the fourth level of British soccer). It was a shocking, exciting, and historic run for Bradford City all the way to the final, finally getting blown out 5-0 to the Swans, who were surprise trophy winners themselves.

If you currently follow a Premier League club that is still playing in the EFL Cup, you will notice that the squad during the week looks much different than it does on the weekend. This is by design for your club's manager. It also means that your club could lose to a side it normally wouldn't lose to.

EFL Cup Draw Format

The format of the tournament can also lead to some surprising results. There is no tournament bracket that is set up before the tournament begins, which is what most American sports fans are used to when they hear about a tournament.

There is also no seeding. Instead, this tournament is drawn round-by-round. Anyone still in the tournament can be drawn against anyone else. It leads to some fun matchups.

For instance, in this current 2016/17 EFL Cup, the fourth round consisted of another Manchester derby. United defeated City, 1-0. In another match, Liverpool beat Tottenham, 2-1. Two top clubs were knocked out by two other top clubs.

Meanwhile, there were two other matches that were played between two clubs that are not in the Premier League. The winners of those matches -- Newcastle and Leeds -- are moving on to the quarterfinals. Because of that, the eight clubs remaining consist of six Premier League sides and two Championship (second-tier) sides.

That can happen when you have a round-by-round draw.

EFL Cup Rewards

While the tournament may not be a priority, every club wants to win a major trophy. The EFL Cup is arguably the least important competition, but it still qualifies as providing a major trophy to the winner.

Furthermore, the tournament is tied to European competition. The winner of the tournament is guaranteed qualification into the Europa League.

For those new to the tournament, there is plenty to make things fun and exciting to watch. With two second-tier clubs still in this year's competition, there might still be a surprise or two out there. All of it together makes for some fun soccer in the middle of the week, which is a always a good thing.